Complementary recording system using multi-scan

ABSTRACT

An image forming apparatus wherein an image for a predetermined region of a recording material is formed using images having a complementary relation by a plurality of scans of a recording head, the apparatus including allocating means for allocating a multi-level image data for the predetermined region for the scans; gradation reducing means for reducing gradation of the multi-level image data allocated by the allocating means, respectively; image forming means for forming an image having the complementary relation by driving the recording head in the scans on the basis of the image data having gradations reduced by the reducing means; wherein the complementary relation of the image by the forming means is reduced by at least one of the allocating means and the gradation reducing means.

BACKGROUND OF THE INVENTION Field of the Invention and Related Art

The present invention relates to an image forming apparatus, an imageforming method and an image processing method for effecting recording ona recording material wherein a density of non-uniformity is attributableto a variation of a recording property among a plurality of recordingelements of a recording head. More particularly, it relates to an imageforming apparatus, an image forming method and an image processingmethod wherein moire or the like is attributable to error in a mountingposition of the recording heads.

An ink jet recording apparatus is known in which a recording headprovided with a plurality of ink ejection outlets, is an example of anapparatus using a recording head that is provided with a plurality ofrecording elements.

In such an apparatus, sizes and/or positions of the dots provided by theink are not uniform due to variations in ejection outlet diameters ofthe ejection outlets and/or ejecting directions, and if this occurs, theprinted image density is not uniform as well. Particularly, in arecording device of a serial type in which the recording head isscanningly moved in a direction that is different from the direction ofthe arrangement of the recording elements, for example, perpendicularthereto, the density of non-uniformity that is attributable to theabove-described variation in the ejection outlet diameters results instripes in the printed image, with the result that the quality of theimage deteriorates.

In order to correct such a density non-uniformity, it has been proposedthat in the image formation using a recording head of an ink jetrecording type, one pixel or pixels of a line corresponding to onescanning of a recording head, is printed by ink ejected from differentejection outlets on the basis of image data which have been processedfor low gradation. This can be done by feeding the sheet through adistance smaller than the width of the recording head and completing onepixel by a plurality of scans for paths.

FIG. 3 shows an arrangement of a conventional ink jet recording head.The printer usable with this recording head forms an image by CMYK inks(four colors). The recording head 601 is provided with two ink jet headsof each ink color, and a head 603 (rear head) disposed at an upperposition in the Figure and a lower head 602 (front head) are disposed ina sub-scan direction with a distance of 2.5 bands (one band is a unit ofa width measured in a direction of the nozzle array operated in one scanof the ink jet head).

FIG. 4 shows an overlaying state of printing using the head 602 and therear head 603 in the printer using the recording head show in FIG. 3.One sub-scan is carried out for one main-scanning. A distance of feedingin the sub-scan direction is one band, so that image is formed withdeviation of half-band between the front head 602 and the rear head 603.Here, the half-band 703 is constituted by the uproar one half of thefront head 602 and the lower one half of the rear head 603, and thehalf-band 704 is constituted by the lower one half of the front head 602and the upper one half of the rear head 603.

Referring to FIG. 5, the description will be made as to the process inwhich the image data of a multi-level type fed to the printer arebinarized, and are converted to head driving data to eject the ink fromthe nozzle.

(1) The image data of the multi-level type transferred from a hostcomputer is stored in an image data storing apparatus 801. The data arefed out from here one by one band.

(2) A pallet conversion circuit 802 separates the image data tomulti-level data of respective ink colors. The description will be madeas to black ink Bk as a representative.

(3) A “gamma” conversion circuit 803-K effects a “gamma” conversion tothe multi-level data separated for each ink color.

(4) A non-uniformity correcting circuit 804-K corrects thenon-uniformity due to the variation in the properties of the nozzles,using a non-uniformity correction table (look-up table for conversionfrom multi-level data to multi-level data).

(5) A binarizing circuit 805-K coverts the multi-level to binary datausing an error diffusion method (ED).

(6) A SMS (sequential multi-scanning) circuit 806-K determines which oneof the front head 602-K and the rear head 603-K is to be used. The SMScircuit, when a certain raster scan is considered, allots the data tothe front, rear, front, rear, namely, alternatingly from the left enddot, and they are outputted to the TMC (Timing Memory Controller)circuits 807-K1, 807-K2. By doing so, it does not occur that adjacentdots are printed by the same head, and the printing operation can becarried out at twice the speed of the driving frequency of the head. Thedot appearing first in each raster scan is printed by the rear head603-K in the case of an odd number raster scan and by the front head602-K in the case of an even number raster scan.

(7) In the TMC circuits 807-K1, 807-K2, the data for one band areoutputted to each head 602-K, 603-K. A positional deviation in themain-scanning direction between the heads 807-K1, 807-K2 is adjustedusing a lateral registration adjusting value, where the output timingfor one array is different depending on the lateral registrationadjusting value.

(8) PHC (Printer/head connector) substrates 808-K1, 808-K2 output thebinary data in the nozzle array direction, corresponding to the nozzleswhich actually effect printing. A positional deviation in the nozzlearray direction between heads 807-K1, 807-K2 is adjusted by thelongitudinal registration adjusting value. The recording head in thisexample has 1344 nozzles and additional upper and lower 8 nozzles whichare effective for printing, and therefore, the longitudinal registrationadjusting value is in the range of −8-+8. When the longitudinalregistration adjusting value is ±0, central 1344 nozzles are used, butwhen the longitudinal registration adjusting value is ±1-8, the actuallyused nozzles are deviated by 1-8 nozzles from the center. The data for1344 nozzles are outputted corresponding to the nozzles to be actuated,using the longitudinal registration adjusting value.

(9) Finally, the binary data for each nozzle are converted to headdriving data by a print control device (Head CPU) 809 to eject the inkfor printing.

Referring to FIG. 7, there is shown the processes (5) and, (6) in moredetail. The multi-level data after the color separation, the “gamma”conversion and the non-uniformity correcting process (802, 803, 804 inFIG. 5) are subjected to an error diffusion process (FIG. 7B) using anerror diffusion matrix A (FIG. 6A) to effect binarization (FIG. 7C). InFIG. 6, the asterisk indicates the noting pixel. By SMS (806 in FIG. 5),the determination will be made as to whether the front head or the rearhead is to be used. The data shown in FIG. 7E is fed to the front head,and the data shown in FIG. 7F are fed to the rear head.

According to the above-described method, an image in the predeterminedregion is formed by different nozzles of two heads, and therefore, thedensity non-uniformity or the like due to variation in the properties ofnozzles can be reduced. In addition, the pitch of the interfaces ishalf-band so that bandings is less conspicuous.

In this manner, the density non-uniformity attributable to theproperties peculiar to the ejection outlets of the ink jet head can bediffused on the recording material, by which the density non-uniformityis reduced. This is called “multi-scan” or “multi-path”. Furthermore, aso-called sequential multi-scan (SMS) system has been proposed in whichthe ink ejection outlets are actuated in a predetermined order mainly tomake the ink ejection outlets uniform.

However, it has been found that there is a point to improve in use witha large scale multi-color ink jet printing apparatus. For example, atextile printing apparatus in which the scanning range is as large asseveral meters, and in addition to the yellow color, magenta color, cyancolor and black color inks, light color and special color inks are used.More particularly, if an ideal apparatus is used with the method, therecorded pixels are uniformly arranged. However, practically, the sizeand/or deposit positions of the dots provided by the ink varies due tothe variation of the ejection outlet diameters of the ink and thevariation of the direction of ejection, and in addition, due tounavoidable error in the mechanical mounting accuracy among recordingheads, the variation in registration occurs between main-scanning.Therefore, the intervals between recorded unit pixels to be overlaid bythe multi-scan are different with the result of moire and/ornon-uniformity with half-scan interval. Particularly, in the case ofreciprocal main-scanning recording, the mounting angle of the recordinghead or the shape of the ejection outlet is different between theforward path and the backward passage with the result beingreciprocation non-uniformity.

The inventor's investigations have revealed that plurality of scans arein complete complementary relation, and this is a cause of the problem.In the above-described method, the half-band images are complementarywith each other, that is, the dots provided by the scans are spatiallycomplementary with each other. Therefore, if an error in registrationoccurs between the bands, for example, when the lateral registration isdeviated by a half dot, the complementation is effected with the lateralregistration remaining.

If the recording is effected using an ideal apparatus and the method,the solid image has uniformly distributed dots without overlapping. InFIG. 8, designated by 21 (black dot) are the dots provided by a firstscanning, and designated by 22 (white dot) are the dots provided by thesecond scanning.

However, in the actual machines, the unavoidable error in the physicalaccuracy results in small change or non-uniformity in the respectivescans, and therefore, when the dots provided by prospective scans areoverlaid, the dots are too close or too remote relative to each other.For example, when a lateral registration of a half dot occurs in thefirst scanning, sparse/dense states or overlapping of dots appear, asshown in FIG. 9.

Designated by 21 (black dots) are the dots printed by the firstscanning, and designated by 22 (white dots) are the dots provided by thesecond scanning. As a result, the printed image is different from theintended image in the image density, that is, the image density is notuniform. More particularly, dark bands and light bands appear (“band” isa unit width in the direction of a nozzle array covered by one scan ofthe ink jet head).

SUMMARY OF THE INVENTION

Accordingly, it is a principal object of the present invention toprovide an image forming apparatus, an image forming method and an imageprocessing method wherein the multi-scan type is used, and a highquality image can be provided at high speed with a reduced densitydifference due to a difference between the unit pixels recorded.

It is another object of the present invention to provide an imageforming apparatus, an image forming method and an image processingmethod wherein the image density does not significantly change even whenthe registration slightly changes due to a physical error, so thatuniform images can be provided with reduced density non-uniformity.

According to an aspect of the present invention, there is provided animage forming apparatus wherein an image for a predetermined region of arecording material is formed using images having a complementaryrelation by a plurality of scans of a recording head, said apparatuscomprising allocating means for allocating a multi-level image data forthe predetermined region for the scans; gradation reducing means forreducing gradation of the multi-level image data allocated by saidallocating means, respectively; image forming means for forming an imagehaving the complementary relation by driving said recording head in saidscans on the basis of the image data having gradations reduced by saidreducing means; wherein the complementary relation of the image by saidforming means is reduced by at least one of said allocating means andsaid gradation reducing means.

With this structure, the images provided by the respective scanningshave less complementary relation or reduced complementary relation sothat even if the registration changes are due to a physical accuracyerror, the image density does not change significantly since thedependency upon the registration is less, and therefore, the uniformitycan be maintained.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating an image print portion of atextile printing machine of an ink jet recording type for printing ontextile, to which the present invention is applicable.

FIG. 2 is a perspective view illustrating in detail a neighborhood ofthe jet print portion A-2 of FIG. 1.

FIG. 3 illustrates arrangement of heads usable with the presentinvention.

FIG. 4 illustrates an overlaying state of the printed images provided bythe front head and the rear head.

FIG. 5 is a block diagram showing processes in which the data suppliedto a conventional printer are printed.

FIGS. 6A and 6B show examples of an error matrix.

FIGS. 7A-7F illustrate a conventional image processing method.

FIG. 8 illustrates positions of dots when the overlaying printing iseffected by the ideal conventional front head and rear head.

FIG. 9 illustrates positions of dots when the overlaying printing easeeffected by an actual conventional front head and rear head.

FIG. 10 is a block diagram showing a process in which the data suppliedto a printer according to the present invention are printed.

FIGS. 11A-11I show specific examples of image processing in Embodiment1.

FIG. 12 shows positions of dots when the overlaying printing is effectedby an ideal front head and rear head according to the present invention.

FIG. 13 shows positions of dots when the overlaying printing is effectedby an actual front head and rear head according to the presentinvention.

FIGS. 14A-14I illustrate specific examples of image processing accordingto Embodiment 2 of the present invention.

FIGS. 15A-15I illustrate specific examples of image processing accordingto Embodiment 3 of the present invention.

FIGS. 16A-16I illustrate specific examples of image processing accordingto Embodiment 4 of the present invention.

FIGS. 17A-17I illustrate specific examples of image processing accordingto Embodiment 5 of the present invention.

FIG. 18 illustrates an overlaying state printed image in each scanningof a printer having one head per color to which the present invention isapplicable.

FIGS. 19A-I show specific examples of image processing according toEmbodiment 6 of the present invention.

FIG. 20 is a sectional view of a full-color ink jet textile printingapparatus using a seventh embodiment of the present invention.

FIG. 21 is a block diagram showing a flow of image data process used inthe seventh embodiment of the present invention.

FIG. 22 is an illustration of a recording method using sequentialmulti-scan, used in the seventh embodiment.

FIG. 23 is a block diagram showing a structure of an executing portionfor the sequential multi-scan used in the seventh embodiment of thepresent invention.

FIG. 24 is a block diagram showing a structure of a random distributionflag generation portion used in the seventh embodiment of the presentinvention.

FIG. 25 is a block diagram showing a structure of an AND-OR matrixportion used in the seventh embodiment of the present invention.

FIG. 26 is a block diagram showing a structure of an executing portionfor the sequential according to the eighth embodiment of the presentinvention.

FIG. 27 is an illustration of a recording method using the sequentialmulti-scan according to the eighth embodiment of the present invention.

FIG. 28 is a block diagram showing a structure of a random distributingflag generator according to the eighth embodiment of the presentinvention.

FIG. 29 illustrates an operation of an AND-OR matrix portion used in theeighth embodiment of the present invention.

FIG. 30 is a block diagram showing the flow of image data processing ina full-color ink jet textile printing apparatus according to the ninthembodiment of the present invention.

FIG. 31 is a block diagram showing a structure of a multi-level SMSexecuting portion used in the ninth embodiment of the present invention.

FIG. 32 illustrates a specific operation of the multi-level SMSexecuting portion and data converter used in the ninth embodiment of thepresent invention.

FIG. 33 is a block diagram showing a structure of a multi-level SMSexecuting portion, a data converter and a binarizing processor accordingto the tenth embodiment of the present invention.

FIG. 34 illustrates specific operations of the multi-level SMS executingportion and the data converter used in the tenth embodiment of thepresent invention.

FIG. 35 is a block diagram showing a structure of a multi-level SMSexecuting portion according to the eleventh embodiment of the presentinvention.

FIG. 36 is a block diagram showing structures of a multi-level SMSexecuting portion, a data converter and are a binarizing processor.

FIG. 37 illustrates specific operations of the multi-level SMS executingportion, the data converter and the binarizing processor according tothe eleventh embodiment of the present invention.

FIG. 38 is a block diagram showing a structure of a multi-level SMSexecuting portion according to the twelfth embodiment of the presentinvention.

FIG. 39 is a block diagram showing structures of the multi-level SMSexecuting portion, data converter and the binarizing processor accordingto the twelfth embodiment of the present invention.

FIG. 40 illustrates specific operations of the multi-level SMS executingportion, the data converter and the binarizing processor according tothe twelfth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the accompanying drawings, the preferred embodiments of thepresent invention will be described. Embodiments 1-3 use a plurality ofcolor heads, which are the same as each other in structure; Embodiment 4uses 4-level processing in place of the binary gradation reduction, andEmbodiment 5 uses one head for the same color.

FIG. 1 is a schematic view of an image printing portion of a textileprinting machine of an ink jet recording type for effecting printing ona textile, to which the present invention is applicable. The printingapparatus comprises a textile feeding portion B for feeding a printmedium such as a rolled textile that has been subjected to a pre-processfor textile printing, a main assembly portion A for printing by means ofink jet heads while the fed print medium is advanced precisely, and awinding-up portion C for drying and winding the printed material up. Themain assembly portion A comprises a precise feeding portion A-1 for theprint medium, the portion A-1 including a platen, and an ink jet print.

The operation will be described with an example in which the textileprinting is carried out on a pre-processed medium.

The pre-processed roller-like print medium 236 is fed out from thefeeding portion H to the main assembly portion. The main assemblyportion is provided with an endless belt 237 which is precisely andstepwise driven and which is extended and stretched around a drivingroller 247 and a winding roller 249. The driving roller 247 is drivenstepwise directly by a stepping motor (not shown) with high resolutionto feed the belt by the stepping distance (pitch). The fed textile 236urged to a surface of the belt 237 backed up by the winding roller 249,by a press-contact roller 240.

The print medium 236 stepwise fed by the belt is correctly positioned bya platen 232 contacted to the back side of the belt at a first printportion 602. Each time the printing operation for one line is completed,the stepping is carried out, and the medium is dried by a heating plate234 from the back side of the belt and by the warm air supplied to thefront side through a warm air duct 235. Subsequently, the overlayingprint is carried out at a second print portion 603 in a similar mannerto that used in the first print portion.

After the printing, the print medium 236 is peeled, and dried again at adrying portion 246 similarly to the heating plate 234 and the warm airduct 235, is guided by a guiding roller 241, and is wound up on awinding roller 248. The print medium 236 is then dismounted from thepresent apparatus, and is subjected to post-processing steps includingcoloring, cleaning and drying steps or the like.

A description will be made as to the ink jet print portion A-2,referring to FIG. 2.

Here, the information is printed with thinned dots by the heads of thefirst print portion, and the medium is subjected to the drying process,and then, is subjected to printing by the heads of the second printportion so as to complement the thinned part by the first print portion.

In FIG. 2, the print medium is stuck on the belt 237 to be steppedupwardly in the Figure. In the Figure, the first print portion 602disposed at a lower petition is provided with a first carriage 244carried four ink jet heads for Y, M, C, K. In this example, the ink jethead (printing heads) uses thermal energy generating elements forcreating film boiling in the ink, to eject the ink.

Downstream of the first print portion, there is provided a dryingstation 245 including a heating plate 234 for heating the medium fromthe back side of the belt and a warm air duct 235 for drying it from thefront side. A heat transfer surface of the heating plate 234 is pressedagainst an endless belt, which is strongly tensioned, and belt 237 isstrongly heated from the back side with high temperature and highpressure vapor through the inner part which is hollow. The belt 237directly and therefore efficiently heat the print medium 236 by the heatconduction. An inside of the heating plate surface is provided with fins234 to catch the heat effectively. The side not contacted to the belt iscovered by a heat insulating material 243 so as to reduce heat loss byradiation.

At the front side, the dried air is supplied from a downstream supplyduct 230, by which the print medium 236 which is being dried is exposedto air having low humidity. The air flows in a direction which isopposite to the feeding direction of the print medium 236, and the airwhich has absorbed the moisture does not condense on the machine devicesbecause of the provision of a suction duct 233, which removes a muchlarger amount of air than the amount of the air supplied thereto. Asupply source of the warm air is disposed at a rear side, and the air issucked a the front side so that pressure difference between the blowingoutlet 238 and the suction opening 239 facing the print medium 236 isuniform over the entire longitudinal area. The air discharge/suctionportion is offset toward downstream from the center of the rear heatingplate 234 so that air is applied to the motion sufficiently heated. Bydoing so, the great amount of the water in the print medium 236 havingabsorbed the ink and thinning liquid at the first print portion 602.

The second print portion 603 is disposed downstream thereof (at theupper side in the Figure), with the second carriage having a structuresimilar to the first carriage. Downstream thereof, there is provided adry portion 46 having a structure similar to the warm air duct 235.

A description will be made as to a specific example of the ink jettextile print. As described in the foregoing, FIG. 1 shows the structureof the ink jet printing apparatus suitable for textile printing. Afterthe ink jet textile printing using the ink jet printing apparatus shownin FIG. 1, the print medium is dried (including air drying as a meansfor doing so). Then, there is provided a step in which the dye in theprint medium fibers continues to diffuse, and is fixed by reaction. Bythis step, sufficient coloring and durability by the fixing of the dyeis provided. The diffusing and reaction fixing step may be of any knowntype, for example, a steaming method. In this case, an alkali processmay be performed before the textile printing process.

Thereafter, non-reaction dye and the substance used in thepre-processing are removed in the post-processing step. Finally, defectcorrection, ironing and other finishing steps are performed to completethe print.

Embodiment 1

In this embodiment, the process is different from the conventional onein which the allocation of the binary data to the front head and therear head is performed after the binarization. More particularly, inthis embodiment, the multi-level data before the binarization areallocated to the front head and to the rear head, and the allocatedmulti-level data are modified with different coefficients, and then, thethus modified or converted data are subjected to the binarization. Byvirtue of this procedure, the complementary relation of the printedimages provided by the scans is reduced, and half-band non-uniformity issuppressed.

Referring to FIG. 10, a description will be made as to the flow ofprocessing from binarization of the multi-level image data to theprinting by ejection of the ink resulting from the conversion of thedata to head driving data.

(1) The image data of the multi-level type transferred from a hostcomputer is stored in an image data storing apparatus 1001, and the dataare fed out from here band by band.

(2) A pallet conversion circuit 1002 separates the image data intomulti-level data of respective ink colors. The description will be madewith black ink Bk as a representative.

(3) A “gamma” conversion circuit 1003-K effects a “gamma” conversion tothe multi-level data separated for each ink color.

(4) The non-uniformity correction circuit 1004-K corrects thenon-uniformity due to the variation in the nozzle properties using anon-uniformity correction table (look-up table formulti-level-to-multi-level conversion).

This process is the same as the conventional process.

(5) distribution circuits 1005-K1, 1005-K2 allocate the data either tothe front head or to the rear head.

(6) data converting circuits 1006-K1, 1006-K2 effect data conversionwith a predetermined coefficient for the allocated data.

(7) gradation reduction circuits 1007-K1, 1007-K2 effect gradationreduction processes for each head using the error diffusion method.

(8) TMC (Timing Memory Controller) circuits 1008-K1, 1008-K2 output thedata for one band for each head one by one nozzle array. A positionaldeviation in the main-scanning direction between the heads is adjustedusing a lateral registration adjusting value, the output timing for onearray is different depending on the lateral registration adjustingvalue.

(9) PHC (Printer/head connector) substrates 1009-K1, 1009-K2 output thebinary data in the nozzle array direction, corresponding to the nozzleswhich actually effect printing. A positional deviation in the nozzlearray direction between heads is adjusted by a longitudinal registrationadjusting value. The recording head in this example has 1344 nozzles andadditional upper and lower 8 nozzles which are effective for printing,and therefore, the longitudinal registration adjusting value is in therange of −8-+8. −8-+8. When the longitudinal registration adjustingvalue is ±0, central 1344 nozzles are used, but when the longitudinalregistration adjusting value is ±1-8, the actually used nozzles aredeviated by 1-8 nozzles from the center. The data for 1344 nozzles areoutputted corresponding to the nozzles to be actuated, using thelongitudinal registration adjusting value.

(10) Finally, the binary data for each nozzle are converted to headdriving data by a print control device (Head CPU) 1010 to eject the inkfor printing.

In this embodiment, the above-described process has been performed usinghardware, but software is usable when it is appropriate.

FIG. 11 shows specific examples of the steps 1005, 1006, 1007 in FIG.10. In FIG. 11, the multi-level data (FIG. 11) are divided into theimage data to be fed to the front head 602 (B) and the data to be fed tothe rear head 603 (C). The divided data are multiplied by differentcoefficients. For example, when the data of the noting pixel is 100,data 100 is allocated to the front head, and data 100 is allocated tothe rear head. Then, the front head data are multiplied by 0.55 (D), andthe rear head data are multiplied by 0.45 (E). At this time, the sum ofthe coefficients is not always one, which will be described hereinafter.In addition, the allocation and conversion of the data are accomplishedby different circuits, but they can be accomplished by a single circuit.

Then, the data thus having subjected to the data conversion arebinarized using the error diffusion method (F and G), and the binarizeddata (H and I) are printed by respective heads.

FIG. 12 shows the results of overlaying printing provided by the frontheads and the rear heads using the image processing method according tothe present invention (solid image), when the physical accuracy isideal. Designated by 21 (black dot) is the result of print by the fronthead, and designated by 22 (white dot) is the result of print by therear head. Designated by 23 (hatched dot) is the result of print by boththe front head and the rear head. There are pixels which are not printeddespite the printing is effected for a solid image, and there are pixelswhich are printed both by the front head and the rear head. This isbecause the multi-level image data are multiplied by differentcoefficients and are independently binarized. This is the result of thereduction of the complementary relation between them.

FIG. 13 deals with the case in which the registration between the fronthead and the rear head is slightly deviated. Here, deviation occurs inthe lateral direction by one half dot. When FIG. 12 and FIG. 13 arecompared, no significant difference is recognized in the image density.In other words, the density hardly changes even when the registrationbetween scans slightly changes, and therefore, the half-pitch bandnon-uniformity does not occur.

In this embodiment, the data of the front head and the data of the rearhead, both of which are multi-level data, are multiplied by differentcoefficients, and then, they are binarized, so that complementationrelationship is reduced. Therefore, the influence of the change in theregistration is reduced, and even when the registration changesslightly, the change or non-uniformity of the image density is smallerwith reduced half-band non-uniformity.

Here, the description has been made with a macroscopic complementaryrelationship using an image provided by a plurality of scans, but thesame applies microscopically. In such a case, when the dots provided bya plurality of scans are noted, it can be said relative relationshipthat adjacent to a dot provided by a scan, no dot is provided by anotherscan.

FIG. 14 shows a specific example of steps 1005, 1006, 1007 in FIG. 10.In FIGS. 14A-D, the multi-level data (FIG. 14A) is allocated to imagedata (FIG. 14B) to be fed to the front head and the image data (FIG.14C) to be fed to the rear head, and the allocated data are multipliedby the same coefficient (0.5) ticket. The data (FIGS. 14D and 14E),having been subjected to the data conversion, are binarized by the errordiffusion method using different error distribution matrixes (FIGS. 14F,14G), and the binarized data (FIGS. 14H and 14I) are printed by therespective heads.

Although the multi-level data from which the data for the front head andthe data for the rear head are the same, the complementary relationbetween the image provided by the heads is reduced so that the half-bandnon-uniformity is reduced in the resultant image, since the errordistribution matrixes for the error diffusion are different from eachother.

Embodiment 3

FIG. 15 shows a specific example of steps 1005, 1006, 1007 shown in FIG.10. In FIGS. 15A-I, the multi-level data (FIG. 15A) are allocated to theimage data (FIG. 15B) to be fed to the front head and the image data(FIG. 15C) to be actuated to the rear head, and the audited multi-leveldata are multiplied by the same coefficient (0.5). The data (FIGS. 15Dand 15E), having been subjected to the data conversion, are binarized byan error diffusion method (FIGS. 15F and 15G) using different thresholdlevels, and the binarized data (FIGS. 15H and 15I) are printed by therespective heads.

Although the multi-level data, from which the data for the front headand the data for the rear head are the same, the complementary relationbetween the images is reduced so that half-band non-uniformity isreduced, since the threshold levels of the error diffusion processes aredifferent from each other.

The same effect can be provided when the elements of Embodiment1-Embodiment 3, are combined (the data conversion for the front and rearheads, the error distribution matrixes of the error diffusion, and thethreshold levels for the binarization).

Embodiment 4

FIG. 16 shows a specific example of states 1005, 1006, 1007 in FIG. 10.In FIGS. 16A-G, the multi-level data (FIG. 16A) are allocated to theimage data (FIG. 16B) for the front head and the image data (FIG. 16C)for the rear head, and the allocated data are multiplied by the samecoefficient (0.6). The data (FIGS. 16D and 16E) having been subjected tothe data conversion, are binarized by an error diffusion method (FIGS.16F and 16G) using different error distribution matrices, and thebinarized data are printed by the respective heads. This embodiment isdifferent from Embodiment 1-3 in that the sum of the coefficients usedin the data conversion process is larger than 1. More particularly, inEmbodiment 4, the sum is 1.2. This means that printing is possible witha duty more than 100%.

In this embodiment, similar to Embodiment 2 the data, having beensubjected to data conversion, are binarized by the error diffusionmethod using different error distribution matrixes, and the binarizeddata are printed by the respective heads. However, the printing with theduty higher than 100% is possible if the use is made with the dataconversion coefficient sum which is larger than 1, in Embodiment 1 andEmbodiment 3. This applies to Embodiments 5 and 6.

Embodiment 5

Referring to FIG. 17, the embodiment will be described in which thegradation reduction is accomplished by use of dot diameter modulationand 4-level processing. This embodiment is the same as Embodiment 1except for the use of 4-level processing as the gradation reductionprocess, and the multi-level data (FIG. 17A) are allocated to the datafor the scanning number of data covering the same area (FIGS. 17H and17C), and the allocated multi-level data are multiplied by differentcoefficients (0.55, 0.45). The converted data (FIGS. 17D and 17E) areconverted to 4-level data by the error diffusion method (FIGS. 17F and17G), and the 4-level data (FIGS. 17H and 17I) are printed by therespective heads.

In the conventional 4-level processing, the complete complementaryrelation is used decay the images provided by the perspective heads.However, according to the present invention, the complementary relationbetween the heads is reduced by which the half-band non-uniformity isreduced in the resultant image.

Similar to Embodiment 1-3, the same effect can be provided by the use ofthe error distribution matrixes or the threshold levels in the errordiffusion method are made different.

Embodiment 6

This embodiment relates to the case where one head is provided for onecolor. Referring back to FIG. 10, the image processing of thisembodiment is realized by replacing the F (front) head with a firstscanning and by replacing the R (rear) head with a second scanning.

FIG. 18 shows an overlaying state in the printed image provided by thefirst and second scans. The feeding distance of the media corresponds tohalf-band, and the image is formed by the first scanning and the secondscanning with half-band overlaying.

FIG. 19 shows a specific example of process corresponding to FIG. 10. InFIG. 19, similar to Embodiment 1-Embodiment 3, the multi-level data(FIG. 19A) are allocated to the number (the number of scans for the samearea) of data (FIGS. 19B and 19C), and the allocated data are subjectedto data conversion with predetermined coefficients (0.55 for the firstscanning, and 0.45 for the second scanning) (FIGS. 19D and 19E). Theconverted data are binarized by the error diffusion method (FIGS. 19Fand 19G), and the binarized data (FIGS. 19H and 19I) are printed throughthe first scanning and the second scanning.

Even when the error occurs in the feeding of the media in the sub-scandirection or when the registration slightly changes, half-bandnon-uniformity is not significant in the image since the complementaryrelation is reduced between the prints provided by the plurality ofscan.

The same effect can be provided when the use is made with the errordistribution matrixes or the threshold levels in the error diffusionmethod similar to Embodiment 1-Embodiment 3.

Embodiment 7

This embodiment shows an example in which the present invention is usedin an ink jet type textile printing machine. FIG. 20 is a sectional viewof a full-color ink jet recording apparatus.

In FIG. 20, reference numeral 100 is a feeding portion for feedingtextile 101 (recording material or medium); 102 is a printer unit foreffecting printing; 103 is a winding unit for winding the recordingmaterial 101 up; 104 is a feeding roller on which the recording material101 is wound; 105, 106 are confining rollers; 107 is a driving roller;108, 109 are platen portions for maintaining the flatness of the printportion; 110 is a confining roller; 111 is a driving roller; 112 is adry portion; 113 is a winding roller; 114 is a support for supportingthe carriage 116; 117 is a motor for scanningly moving the carriage unitin the main scan direction. Driving rollers 107 and 111 are driven bythe conveyor belt 118, which is stretched between the driving rollers107 and 111 with the scanning region of the carriage unit 116therebetween, and adhesive material is applied on the outside surfacethereof. When the rollers are driven by the feeding motor 115, thebonding strength and frictional force relative to the recording material101 function to assist the carrying of the recording material in thedirection A.

The carriage unit 116 moves in the horizontal plane above the post 114by the carriage motor 117. Then, the printing is carried out by the inkjet head 119-134 provided on the unit 116. The elements 119-126 aredisposed at an upstream side in the feeding path of the recordingmaterial 101, namely, closer to the feeding roller 102. Referencenumeral 119 is a first magenta head provided with a plurality ofejection outlets for effecting magenta ink; 120 is a first yellow headfor ejecting a yellow ink; 121 is a first orange head for ejectingorange ink; 122 is a second light magenta head for ejecting lightmagenta ink; 123 is a first cyan head for ejecting cyan ink; 124 is afirst light cyan head for ejecting light cyan ink; 125 is a first bluehead for ejecting blue ink; 126 is a first black head for ejecting blackink.

The ink jet heads 127-134 are disposed at a downstream side in thefeeding path for the recording material, namely after the ink jet head119-126. It is disposed such that scans of the ink jet heads 127-134 andthe ink jet heads 119-126 are deviated by a distance which is one halfof the width. Thus, they are defeated by 0.5 band with. Among thoseheads, reference numeral 127 is a second magenta head for ejectingmagenta ink; 128 is a second yellow head for ejecting yellow ink; 129 isa second orange head for ejecting orange ink; 130 is a second lightmagenta head for ejecting light magenta ink; 131 is a second cyan headfor ejecting cyan ink; 132 is a second light cyan head for ejectinglight cyan ink; 133 is a second blue head for ejecting blue ink.

Therefore, in this embodiment, 8 sets of the recording heads forejecting 8 different color inks, and the corresponding recording headsare deviated by 0.5 band width in the recording material 101 feedingdirection. The cyan and magenta images are formed by dark cyan ink andlight cyan ink, dark magenta ink and magenta ink.

FIG. 21 is a block diagram of a control system used in the ink jetprinter shown in FIG. 20. In FIG. 21, reference numeral 201 is a hostcomputer for controlling the ink jet textile printing system.

The printed image data are transferred from the host computer whose GPIB(General Purpose Interface Bus) interface, are temporarily stored inframe memory 203 under the control of the CPU202. The CPU203 isresponsive to a print start command produced by the host computer toread out of the printed image data in the frame memory 203 by the amountcorresponding to one scanning width through a multi-level/binaryexchange portion 204 to the sequential multi-scan portion 205. Thesequential multi-scan portion 205 allocates the printed image data tofirst band memory 206 and second band memory 207. The image data in thefirst band memory 206 and the second band memory 207 are read out inaccordance with a unidirectional printing or bi-directional printingsequence, and are printed by the first print head 208 corresponding tothe ink jet heads 119-126 in FIG. 1, and the second print head 209corresponding to the ink jet heads 127-134 in FIG. 1. From the secondband memory 207, the image data are supplied to the second print head209 with the time delay corresponding to 0.5 band width so that therelative position in the width scan direction of the first print head206 and the second print head 207.

FIG. 22 shows a printing process by the printer unit 102 of the ink jettextile printing shown in FIGS. 20 and 21.

Here, the first print head 208 connected to the first band memory isdisposed on the upstream side with respect to the feeding direction Y ofthe recording material, and effects the first print on the recordingmaterial 101.

In the printing operation, the image is recorded or printed inaccordance with the recording data in the first band memory 206 providedby allocation algorithm of the sequential multi-scan. Using all of theejection outlets of the first print head 208, the recording is effectedon the portion 301 a of the recording material by the forward scan Xa.

The recorded or printed portion 301 a is fed through a predicamentdistance corresponding to the width of the ejection outlet arrangementof the head, and is then placed as a region 301 b for the recording ofthe second print head 209. For the region 301 b, the printing iseffected by the second print head in accordance with the recording datain the second band memory 207 allocated through the multi-scan type. Asdescribed in the foregoing, the positions of the first print head 208and then second print head 209 are deviated from each other by ½ thewidth L of the ejection outlet array. Therefore, the upstream half ofthe ejection outlets of the second print head 209 are used, and theprinting in the backward scan Xb is effected on the region 302Acorresponding to the downstream half of the region 301 b already printedby the first print head.

Then, the recording material is fed by a distance corresponding to thewidth L of the ejection outlet array, and when the region 301 b of therecording material 101 is placed as a region 301 c, the printing iseffected by the forward scan Xa on the upstream half region 301B of theregion 301 c already printed by the first print head 208, using thedownstream half of the ejection outlet of the second print head 209. Inthis manner, the printing is carried out, the region printed by thefirst print head 208 and the second print head 209 are indicated byreference numeral 302.

As described in the foregoing, in this embodiment using the multi-scantype, the respective lines in the region 302 are printed by the inksejected through different ejection outlets of the first print head 208and the second print head 209. In other words, the data for printing aredivided for the first and second printing heads 208 and 209, and theareas printed by the first print head 208 and the second print head 209are different (the upstream half and the downstream half), so thatdensity non-uniformity and/or the strikes due to the variations in theejection outlet diameters and the ejecting directions or the like of theejection outlets can be diffused.

FIG. 23 is a block diagram of a circuit in the sequential multi-scanportion 205 for allocating and supplying the recording data inaccordance with the multi-scan type shown in FIG. 22. Here, therecording data are allocated to the first magenta head 119 and to thesecond magenta head.

In FIG. 23, a random distributing flag generator 401 produces firstallotting flag (EN1) and second allotting flag (EN2) in synchronism withsynchronization clock φ1 for the transfer of the recording data, fromthe random number generation clock φ2 and φ3 (φ1≠φ2≠φ3). The results oflogical AND processing of the allotting flags and the recording data aresupplied to the first band memory 206 or to the second band memory 207,thus allotting the recording data.

At this time,

(1) when EN1=“H”, EN2=“L”;

The data are allocated only to the first print head 208.

(2) when EN1=“L”, EN2=“H”;

The data are allotted only to the second print head 209.

(3) when EN1=“H”, EN2=“H”;

The data are allotted to both of the first print head 208 and the secondprint head 209.

(4) when EN1=“L”, EN2=“L”;

The data are not allotted to any (the recording data output is L).

In this embodiment, the recording data are outputted with a randomswitch by the synthesizing portion 402 in synchronism with thesynchronization clock φ1 for the transfer of the recording data inaccordance with the allotting flag which is produced at random. Thesynthesizing portion 402 has a 1-bit structure, but the recording datais transferred by an 8-bit unit. Therefore, it is provided with inputbuffer (parallel/serial) and output buffer (serial/parallel).

FIG. 24 is a block diagram of the random allotting flag generator 401.

In this embodiment, 256 non-synchronization clock φ2, φ3 are produced bycounters 501 and 502, respectively. They are subjected to thediscrimination by the AND-OR matrixes 503, 504, 505, 506 to determinethe occurrence probability for each of the above-described said (1),(2), (3) and (4). FIG. 25 shows a block diagram and a table used in theAND-OR matrixes 503, 504, 505, 506.

According to this structure, when the count is 0-63, 128-159, 224-231 or254, the flag signal F indicative of feed of the image data only to thefirst band memory 206 in the AND-OR matrix 503. The occurrenceprobability is approximately 41% (105/256=41.015625%).

When the count is 64-127, 160-191, 232-239 or 255, the flag signal R isindicative of the feed of the image data only to the second band memory207. The occurrence probability is approximately 41%(105/256=41.015625%).

When the count is 192-223, 240-247, 252 or 253, a flag signal Bindicative of feed of the image data to both of the first band memory206 and the second band memory 207. The occurrence probability isapproximately 16.4% (42/256=16.40625%).

When the count is 248-251, the flag signal B indicative of no feed ofthe image data in the AND-OR matrix 506. The occurrence probability isapproximately 1.6% (4/256=1.5625%).

In this embodiment, by changing the structure of the AND-OR matrix 503504, 505, 506, the occurrence probabilities in (1), (2), (3) and (4) canbe selected with gradation of approximately 0.39% (0.390625%).

Referring back to FIG. 12, it may be deemed as a result of overlayingprinting using the first print head and the second print head inaccordance with the image processing method of the present invention inthe case of the solid image on the assumption that physical accuracy isideal. In this case, black dot 21 indicates the prints provided by thefirst print head, and white dot 22 indicates the prints provided by thesecond print head. Reference numeral 23 indicates the prints provided byboth of the first print head and the second print head. There arenon-print pixels, or there are pixels, which are printed by both of thefirst print head and the second print head, despite that image datarepresent a solid image. This is because the occurrence probabilities of(1), (2) are not 0. In this manner, the complementary relation isreduced.

Referring back to FIG. 13, it can be deemed as being the result when theregistration is slightly deviated between the first print head and thesecond print head. In this case, the first print head is deemed as beinglaterally deviated by a half dot. When FIG. 12 and FIG. 13 are compared,it will be understood that change of the image density is significant.Therefore, it is understood that even if the registration slightlychanges, the density hardly changes so that half-band non-uniformity isnot produced.

In this embodiment, similar to the conventional example, the binarizedimage data are allotted, but the data are allotted or not allocated atrandom to the first print head and the second print head, so that thecomplementary relation is reduced. Therefore, the influence of thechange in the registration is small, so that image density change issmaller than in the case of the complete complementary relation, whenthe registration changes slightly. Therefore, the images can be formedwith reduced half-band non-uniformity.

As described in the foregoing, the difference of the interval betweenunit recording elements overlaid through multi-scan due to the error inthe mounting accuracy among the recording heads, can be diffused, sothat moire effect and/or the half-scan pitch non-uniformity can bereduced.

Embodiment 8

FIG. 26 is a block diagram of another structure of the sequentialmulti-scan for allotting and supplying the recording data in accordancewith the multi-scan type shown in FIG. 22. Here, the recording data areallotted to the first magenta head 119 and the second magenta head 127.

In FIG. 26, the same reference numerals as in FIG. 23 are assigned tothe elements having the corresponding functions, and the detaileddescription is omitted for simplicity. In FIG. 26, reference numeral 701is an image data signal; 702 is a signal indicative of image data wherethe effective period in one main-scanning is synchronized with the imagedata signal; 703 is a signal indicative of image data in an effectiveperiod in a raster scan line synchronized with image data signal; 704 isa main-scanning direction discrimination portion which counts theeffective period signal 702 of the image data in one main-scanning fromthe start of the printing operation to discriminate whether the count isan odd number or an even number; 705 either ejecting positiondiscrimination portion for counting the effective period signal 703 ofthe image data in the raster scan line to discriminate whether theejecting position of the image data is at the upstream half or thedownstream half of the recording head. FIG. 27 is an illustration of anoperation of the random allotting flag generator 706 in FIG. 26. Here,the first print head 208 repeats forward printing, backward printing,forward printing, backward printing with reciprocal movement thereof.The second print head 209 effects the first forward print by theupstream half of ejection outlets in the second forward printingoperation of the first print head 208, when the mounting position of thesecond print head 209 is 1.5 times the band width away, and thereafter,it repeats the backward path, the forward print, the backward print andso on. Therefore, the overlaying print condition in terms of themain-scanning directions of the first print head and the second printhead are the following four:

First print head=forward path+second print head=forward path . . . 81

First print head=forward path+second print head=backward path . . . 82

First print head=backward passage+second print head=backward path . . .83

First print head=backward passage+second print head=forward path . . .84

And, from the start of the printing attention, the following isrepeated:

81->82->83->84->81->82->83

FIG. 28 is a block diagram of the random allotting flag generated 706.

In this embodiment, there are provided four AND-OR matrixes 901, 902,903, 904 corresponding to the overlaying print conditions 81-84 in termsof the main-scanning directions of the first print first print head andthe second print head, and the occurrence probability of the allottingconditions said (1)-(4) is switched during the printing operation.

FIG. 29 shows an example of setting in the AND-OR matrix group 901, 902,903, 904. This example is suitable for the case of the followingprinting properties of the recording head:

Density in the forward path print<density in the backward path print.

By setting the allocation in the forward path print which is relativelyhigh, the density difference between the forward scan and the backwardscan is avoided.

In the condition 81 (first/second: forward path/forward path), theprobability of allocation to the first print head 208 and the secondprint head 209 is both approximately 10%, so that print density israised to 110%, by which the density decrease in the forward pathprinting is prevented.

In the condition 82 (first/second: forward path/backward passage), theprobability of allotment to the second print head 209 is lowered toprovide the print density of 100%, and the backward print frequency ofthe second printing head 209 is reduced to approximately 45%.

In the condition 83 (first/second: backward passage/backward passage),the probability of non-allotment either to the first printing head 208or the second printing head 209 is approximately 10%, so that printdensity is lowered to 90%, by which the density rise in the backwardpath printing is suppressed.

In the condition 84 (first/second: backward passage/forward path), theprobability of allotment to the first print head 208 is lowered toprovide the print density of 100%, and the backward print frequency ofthe first printing head 208 is reduced to approximately 45%.

According to this embodiment the difference of the interval between theunit recorded pixel overlaid by the quantitative multi-scan due to themechanical mounting accuracy difference between the recording heads, canbe diffused, so that moire effect and/or the half-scan non-stripes canbe reduced, and in addition the reciprocation non-uniformity due to thedifference in the printing properties between the forward path and thebackward passage, can be corrected.

In the foregoing Embodiments 7 and 8, the recording head includes thefirst and second heads with deviation in the sub-scan direction, and theimage is formed by a plurality of scans for a predetermined region ofthe recording material by these heads. The present invention, however,is not limited to this example, but the plurality of scans can beaccomplished by feeding the recording material through a distancesmaller than the recording width of the recording head.

In the Embodiments 7 and 8, the image data are allotted to the pluralityof (2) band memories by the random allocation flag generator, but as analternative, independent random number generators may be providedcorresponding to the plurality of band memories, and the image data maybe allocated on the basis of the random number produced by therespective random number generators. In this case, the allocation iseffected on the basis of the independent random numbers, so thatcomplementary relation of the image data allotted to the memories is notcomplete.

What is important is that when the image data is allocated at random tothe plurality of memories, the complementary relation of the imagesprovided by the memories is not complete.

Embodiment 9

The fundamental structure in Embodiment 9 is similar to that ofEmbodiment 7 shown in FIG. 20.

FIG. 30 is a block diagram showing a control system of an ink jetprinter according to this embodiment. In FIG. 30, reference numeral 2001is a host computer for controlling the ink jet textile printing system.

From the host computer, GPIB (General Purpose Interface Bus) the printedimage data are temporarily stored in a frame memory 2003 in accordancewith CPU2002. The CPU2002 reads out the data corresponding to onemain-scanning width from the printed image data stored in the framememory 2003 in accordance with the print start command produced by thehost computer. The read out pallet data are converted to multi-leveltone gradation image data corresponding to the coloring property of theink color, by the pallet conversion portion 2004. The thus convertedmulti-level tone gradation image data are then subjected to so-called“gamma” conversion corresponding to the basic ejection property of therecording head for each head by a “gamma” correction portion 2005, andthe ejection property peculiar to the recording head is corrected by anon-uniformity correcting portion 2006.

Then, the multi-level SMS portion 2007 allocates the data to the firstrecording head 2014 and the second recording head 2015.

The allocated multi-level tone gradation image data are subjected to aconversion process with the allocation coefficient by the first dataconverter 2008 and the second data converter 2009, and to thebinarization of an error diffusion method using the error matrix andthreshold at the first and binarization process portion 2010 and secondbinarization process portion 2011. The binary image data are stored in afirst band memory 2012 and a second band memory 2013, and are read outin accordance with a unidirectional printing or bi-directional printingsequence under the control of the CPU2002, so that recording is effectedby the first printing head 2014 and second printing head 2015.

The printing operation of the printer unit of the ink jet textileprinting apparatus is the same as FIG. 22.

FIG. 31 is a block diagram showing a structure of a multi-level SMSportion 207 for allocating and supplying the multi-level gradation datethrough the multi-scan type process. The description will be made as tothe case in which the recording data are located to the first magentahead and to the second magenta head.

In FIG. 31 a random distributing flag generator 401 produces firstallotting flag (EN1) and second allotting flag (EN2) in synchronism withsynchronization clock φ1 for the transfer of the recording data, fromthe random number generation

clock φ2 and φ3 (φ1≠φ2≠φ3). The results of logical AND processing of theallotting flags and the recording data are supplied to the first dataconverter 2008 or to the second data converter 2009, thus allotting therecording data. At this time,

(1) when EN1=“H”, EN2=“L”:

The data are allocated only to the first data converter 2008:

(2) when EN1=“L”, EN2=“H”:

The data are allocated only to the second data converter 2009:

(3) when EN1=“H”, EN2=“H”:

The data are allocated to the first data converter 2008 and the seconddata converter 2009, equally:

(4) when EN1=“L”, EN2=“L”:

The data are not allotted either to the first data converter 2008 or tothe second data converter 2009. (The multi-level tone gradation imagedata output is “L”.)

In this embodiment, the recording data is rewritten at random by thesynthesizing portion 402 and are outputted, in synchronism with thesynchronization clock φ1 for the transfer of the recording data inaccordance with the allocating flag outputted at random in accordancewith the allocation conditions distribution condition (1)-(4). Thesynthesizing portion 402 in FIG. 31 has a 1-bit structure, and it isconstituted by 8-bits for the magenta color. The difference from FIG. 23is in that in this embodiment, the image data are eight bits data, whichare allocated; in FIG. 23, however, the data are 1-bit data for onepixel.

The block of the random allocation flag generator 401 is the same aswith FIG. 24.

The structure of the AND-OR matrix 503 504, 504, 506 is the same as withFIG. 25, and the occurrence probabilities of (1), (2), (3) and (4) canbe selected with gradation of approx. 0.39% (0.390625%). Differentconversion coefficients are multiplied to the allocated data using alook-up table (LUT) in the first data converter 2008 and the second dataconverter 2009.

For example, in the specific example shown in FIG. 32, the multi-levelgradation adjusting value for the noted pixel of the multi-levelgradation image data allocated at random is multiplied by a dataconversion coefficient F1=110 for the first print head 2014 by the firstdata converter 2008, and by a date conversion coefficient F2=0.90 forthe second print head 2015 by the second data converter 2009. However,the sum of the coefficients is not 2. By adjusting the sum, the densityof the image can be adjusted. The processing is carried out in exactsynchronism with the speed of the image data transfer, and the data aresupplied to the first binarization process portion 2011 and the secondbinarization process portion 2012.

In this embodiment, the multi-level tone gradation image data overlaidby quantitative multi-scan is allocated at random for unit pixel, sothat the complementing relation value is reduced, that is,non-complementation is accomplished. Therefore, the difference in theinterval between unit recorded pixels due to the mechanical mountingaccuracy difference between the recording heads can be diffused, so thatmoire effect and/or the half-scan non-uniformity can be reduced.

Embodiment 10

FIG. 33 is a block diagram of a multi-level SMS process portion 2007 anda first data converter 2008 or a second data converter 2009 used inEmbodiment 10. Here, the same reference numerals as in FIG. 30 areassigned to the elements having the corresponding functions, and thedetailed description thereof has been omitted.

In the multi-level SMS process portion 2007, the multi-level tonegradation image data are equally allocated to the first printing head2014 and the second printing head 2015.

The first data converter 2008 and the second data converter 2009 havelook-up tables (LUT) 2801 and 2802 having different values so thatmulti-level tone gradation image data allocated are multiplied by effectcoefficients.

In the first binarization process portion 2010 and the secondbinarization process portion 2011, each image data having been subjectedto the data conversion, are further subjected to binarization processingusing an error diffusion method with different thresholds Th1 (2805) andTh2 (2806) and diffusion toward the marginal pixels using the errordiffusion matrix A (2803) and error diffusion matrix H (2804) havingdifferent structures.

For example, in FIG. 34, the multi-level gradation adjusting value (80)of the noting pixel having an 8-bit structure is multiplied by a dataconversion coefficient F1=0.55 (2801) for the first band by the firstdata converter 2008, and is multiplied by a data conversion coefficientF2=0.45 (2802) for the second head by the second data converter 2009. Atthis time, the sum of the coefficients is not always 1. The processingoperations are carried out in exact synchronism with the image datatransfer speed, and the data are supplied the first binarization processportion 2010 and to the second binarization process portion 2011.

In the first binarization process portion 2010, 5/32 or 9/32 of thenoting pixel value is added to the neighborhood by the error diffusionmatrix A (2803), and in the second binarization process portion 2011,1/8 or 2/8 is added to the neighborhood of the noting pixel by the errordiffusion matrix B (2804). Thereafter, the binarization is carried outin the first binarization process portion 2010 using the thresholdTh1=135 and in the second binarization process portion 2011 using thethreshold Th2=175 in synchronism with the image transfer speed.

According to this embodiment, the multi-level tone gradation image datato be overlaid through quantitative multi-scan are equally allocated,and therefore, the image data immediately after the deduction have acorrelation. However, since the data conversion coefficients, thestructures of the error diffusion matrix, and the binarized thresholds,are different distinctive, the complementary relation provided by themulti-scan is significantly reduced, by which the qualitative differencecan be diffused with the result of reduction of the half-scan intervalnon-uniformity.

Embodiment 11

FIG. 35 is a block diagram showing a structure of a circuit forallocating the recording data to the first magenta head 119 and secondmagenta head 127 in the multi-level SMS portion 2007 in this embodiment.Here, the same reference numerals as in FIG. 30 are assigned to theelements having the corresponding functions, and the detaileddescription thereof are omitted for simplicity.

In FIG. 35, the multi-level tone gradation image data are shifted downby one bit approximately down to ½ level, and are inputted to the first+1 adder 1001 and to the second +1 adder 1002. The bit shift is carriedout by shifting the output of the flip-flop 1000 to the first, andsecond adders 1001, 1002. The lowest bit b0 overflowed by the 1 bitshift-down, is alternately added in the form of 1 bits input to thefirst +1 adder 1001 and second +1 adder 1002 in synchronism with theimage data transfer synchronization clock φ1. By doing so, the first,and second adders 1001, 1002 add the fractions resulting from dividingthe data by 2.

FIG. 36 shows a specific example of the processes of a multi-level SMSprocess portion 2007, a first data converter 2008, and firstbinarization process portion 2010, or a second data converter 2009 and asecond binarization process portion 2011.

Here, the same reference numerals as in FIG. 30 are assigned to theelements having the corresponding functions, and the detaileddescription thereof are omitted.

The multi-level tone gradation image data are substantially equallydivided into the data for the first printing head 2014 and the data forthe second printing head 2015 by the multi-level SMS process portion2007, and the data are supplied to the first data converter 2008 and tothe second data converter 2009. The first data converter 2008 and thesecond data converter 2009 have different look-up tables (LUT) 2801 and2802, so that different coefficients are multiplied to the allocatedmulti-level tone gradation image data. At this time, the densities forthe heads are converted by the look-up tables (LUT) 2801 and 2802 in thefirst data conversion allocator 2008 and second data converter 2009.

In the first binarization process portion 2010 and the secondbinarization process portion 2011, the respective image data converted,are subjected to binarization processing using the error diffusionmethod with different thresholds and error diffusion matrixes havingdifferent structures.

In the specific example of processing shown in FIG. 37, the multi-levelgradation adjusting value of the noting pixel of the multi-level tonegradation image data allocated by ½, for example, 80 is multiplied by adata conversion coefficient F1=1.15 for the first printing head 2014 bythe first data converter 2008 (2801), and multiplied by a dataconversion coefficient F2=0.85 for the second printing head 2015 by thesecond data converter 2009 (2802). However, the sum of the coefficientsis not 2. The processing is carried out in exact synchronism with thespeed of the image data transfer, and the data are supplied to the firstbinarization process portion 2010 and to the second binarization processportion 2011.

In the first binarization process portion 2010, 5/32 or 9/32 of thenoting pixel value is added to the neighborhood of the noting pixelindicated by asterisk in the Figure by the error diffusion matrix A(2803), and in the second binarization process portion 2011, 1/8 or 2/8of the noting pixel value is added to the neighborhood of the notingpixel by the error diffusion matrix B (2804), so that data are diffusedto a plurality of pixels. Thereafter, the binarization is carried out insynchronism with the image transfer speed in the first binarizationprocess portion 2010 using the threshold Th1=135 and in the secondbinarization process portion 2011 using the threshold Th2=175.

According to this embodiment, the multi-level tone gradation image datato be overlaid by the qualitative multi-scan are allocated substantiallyto ½, and therefore, the image data immediately after the dataallocation have a substantial correlation. However, since the dataconversion coefficients, the structures of the error diffusion matrixand the binarized thresholds, are different, respectively, after theallocation, the complementary relation provided by the multi-scan issignificantly reduced, so that quantitative difference can be diffusedwith the result of retention of half-scan pitch non-uniformity.

In this embodiment, the structures of first, and second data convertersand the first, and second binarization process portion, are madedifferent, but since the binarizing processor uses the error diffusionmethod, the difference is not inevitable. This is because even if theallocated image data involved a correlation, the correlation is reducedby the binarization.

Embodiment 12

FIG. 38 is a block diagram showing a structure of the circuit forallocating the recording data to the first magenta head 119 and to thesecond magenta head 127 in the multi-level SMS portion 2007 in thisembodiment. Here, the same reference numerals as in FIG. 30 are assignedto the elements having the corresponding functions, and the detaileddescription thereof are omitted.

In FIG. 38, the alternating allocation flag generator 1301 generatesalternately a first allocation flag (EN1) and a separate allocation flag(EN2) synchronized with the image data transfer synchronization clockφ1. A logical AND of the alternating allocation flag and the recordingdata is calculated and the resultants are alternately supplied to thefirst data converter 2008 or to the second data converter.

FIG. 39 shows a specific example of processes of the multi-level SMSprocess portion 2007, the first data converter 2008 and the firstbinarization process portion 2010 or the second data converter 2009 andthe second binarization process portion 2011. Here, the same referencenumerals as in FIG. 30 are assigned to the elements having thecorresponding function, and the detailed description thereof areomitted.

The multi-level tone gradation image data are allocated toward the firstprinting head 2014 and toward the second printing head 2015 for eachpixel by the multi-level SMS process portion 2007, and are supplied tothe first data converter 2008 and to the second data converter 2009. Thefirst data converter 2008 and the second data converter 2009 havelook-up tables (LUT) 2801 and 2802 having different levels such thatmulti-level tone gradation image data are multiplied by differentcoefficients.

In the first binarization process portion 2010 and the secondbinarization process portion 2011, the image data having been subjectedto the data conversion are further subjected to binarization processingusing the error diffusion method with the error diffusion matrixeshaving different structures and using different thresholds.

FIG. 40 shows a specific example of the process of the first dataconverter 2008, the first binarization process portion 2010, the seconddata converter 2009, the second binarization process portion 2011. Here,the same reference numerals as in FIG. 30 are assigned to the elementshaving the corresponding functions, and the detailed description thereofhas been omitted for simplicity.

In the specific example shown in FIG. 40, for example, the multi-levelgradation adjusting value of the noting pixel having a 8 bit structure,80, for example, is multiplied by data conversion coefficient F1=1.20 bythe first data converter 2008 (2801), and is multiplied by dataconversion coefficient F2=0.80 for the second head direction by the 2009(2802). At this time, the sum is not always 2. The processing is carriedout in exact synchronism with the speed of the image data transfer, andthe data are supplied to the first binarization process portion 2010 andto the second binarization process portion 2011.

In the first binarization process portion 2010, 5/32 or 9/32 of notingpixel value are added to the pixels adjacent the noting pixel indicatedby asterisk by the error diffusion matrix A (2803), and in the secondbinarization process portion 2011, 1/8 or 2/8 of the noting pixel valueis added to the neighborhood of the noting pixel by the error diffusionmatrix B (2804), so that data are diffused to a plurality of pixels.Thereafter, the binarization is carried out in synchronism with theimage transfer speed in the first binarization process portion 2010using the threshold Th1=140 and in the second binarization processportion 2011 using the threshold Th2=180.

According to the embodiment, the multi-level tone gradation image datato be overlaid by quantitative multi-scan are alternating allocated foreach pixel, and the image data after the data distribution importance acorrelation. However, since the thresholds of the error diffusionmatrixes are different, and the alternating allocation results inremarkable differences, the complementary relation provided by themulti-scan is reduced, and therefore, the quantitative differences canbe diffused with the result of reduced half-scan pitch non-uniformity.

In addition, the examples from Embodiment 9 to Embodiment 12 can beproperly combined to enhance the effect of reduction of thenon-uniformity.

The description will be made as to the steps of textile printing carriedout by the recording device having the above-described structures. Afterthe ink jet printing process using the recording apparatus of the inkjet type, the textile is dried (including air drying).

And subsequently, a step of diffusing and fixing therein coloring mattersuch as a dye in the ink deposited on the fibers of the cloths, usingmeans for fixing such coloring matter contained in the ink. This stepcan allow sufficient coloring and fastness to be given due to fixationof dye.

The diffusion and fixation step (including a dye diffusion step and afixing and coloring step) may be any of the conventional well-knownmethods, including a steaming method (e.g., treated at 100° C. under awater vapor atmosphere for ten minutes). In this case, before thetextile printing, the cloths may be subjected to alkaline pretreatment.

Thereafter, in the additional step, unreacted dye and substances used inthe pretreatment are removed. Finally, the finishing step such as defectcorrection and ironing is passed through to complete the printing.

In particular, the cloths for ink jet textile printing are required tohave the properties of:

(1) being colored with the ink at sufficient densities.

(2) having high dyeing rate of ink

(3) rapidly drying the ink on the cloths

(4) causing less irregular blurs of ink on the cloths

(5) having excellent conveyance capability within the apparatus

To meet these requirements, the cloths may be pre-treated as necessaryby using means for adding a treatment agent in this invention. Forexample, in Japanese Laid-Open Patent Application No. 62-53492, severalkinds of cloths having the ink receiving layer have been disclosed, andin Japanese Patent Publication No. 3-46589, the cloths containing areduction inhibitor or alkaline substances have been proposed. Theexamples of such pre-treatment may include treating the cloths tocontain a substance selected from alkaline substance, water solublepolymer, synthetic polymer, water soluble metallic salt, urea, andthiourea.

Examples of alkaline substance include alkaline metal hydroxide such assodium hydroxide and potassium hydroxide, amines such as mono-, di-, ortri-ethanolamine, and carbonic acid or alkaline metal bicarbonate suchas sodium carbonate, potassium carbonate and sodium bicarbonate.Further, they include organic acid metallic salt such as calcium acetateand barium acetate, ammonia and ammonium compounds. Also, sodiumtrichloroacetae which becomes alkaline substance under dry heating maybe used. Particularly preferable alkaline substance may be sodiumcarbonate and sodium bicarbonate for use in coloring of reactive dye.

Examples of water soluble polymers include starch substances such ascorn and wheat fluor, cellulose substances such as carboxymethylcellulose, methyl cellulose and hydroxyethyl cellulose, polysaccharidessuch as sodium alginate, gum arabic, locust bean gum, tragacanth gum,guar gum, and tamarind seeds, protein substances such as gelatine andcasein, and natural water soluble substances such as tannin and lignin.

Also, examples of synthetic polymers include polyvinyl alcoholcompounds, polyethylene oxide compounds, acrylic acid type water solublepolymer, and maleic anhydride type water soluble polymer. Among them,polysaccharide polymer and cellulose polymer are preferable.

Examples of water soluble metallic salts include compounds having a pHof 4 to 10 and making typical ionic crystals such as halides of alkalinemetal and alkaline earth metal. Typical examples of such compoundsinclude alkaline metals such as NaCl, Na₂SO₄, KCl and CH₃COONa, andalkaline earth metals such as CaCl₂ and MgCl₂. Among them, salts of Na,K and Ca are preferable.

The method of pre-treating the cloths to contain any of the above-citedsubstances is not specifically limited, but may be any one of dipping,pad, coating, and spray methods.

Further, since the textile printing ink applied to the cloths for inkjet textile printing may only adhere to the surface of the cloths in thejetted state thereto, the fixation process of fixing a coloring matterin the ink such as a dye onto the fibers is subsequently performed aspreviously described. Such fixation process may be any one ofconventionally well-known methods, including, for example, a steamingmethod, an HT steaming method, or a thermofix method, and if not usingthe cloths pretreated with alkali, an alkali pad steam method, an alkaliblotch steam method, an alkali shock method, and an alkali cold fixmethod.

Further, the removal of unreacted dye and substances used inpretreatment can be made by washing the printing medium in the water orhot water having neutral detergent dissolved therein, using means forwashing the printing medium, by any of conventionally well-known methodsafter the fixing process. Note that it is preferable to use any one ofconventional well-known fixation processes (for the fixation of fallingdye) jointly with the washing.

It should be noted that the printed products subjected to the additionalprocess as above described are then cut away in desired size, cut piecesare subjected to the process for providing the final articles such asstitching, bonding, and welding, to provide the clothes such as aone-piece dress, a dress, a necktie or a swimming suit, a bedclothescover, a sofa cover, a handkerchief, and a curtain. A number of methodsfor processing the cloths by stitching or otherwise to provide theclothes or other daily needs have been well-known.

The printing medium may be textile, wall textile, thread for embroidery,wall paper, paper for OHP film, plate-like member such as almite plate,and other various materials usable with the ink jet technique, and thematerial, weaving method, knitting methods of the textile may be any,and woven fabric and nonwoven material or the like are usable.

The present invention is particularly suitable for use in an ink jetrecording head and recording apparatus wherein thermal energy generatedby an electrothermal transducer, a laser beam or the like is used tocause a change of state of the ink to eject or discharge the ink. Thisis because the high density of the picture elements and the highresolution of the recording are possible.

The typical structure and the operational principle of such devices arepreferably the ones disclosed in U.S. Pat. Nos. 4,723,129 and 4,740,796.The principle and structure are applicable to a so-called on-demand typerecording system and a continuous type recording system. Particularly,however, it is suitable for the on-demand type because the principle issuch that at least one driving signal is applied to an electrothermaltransducer disposed on a liquid (ink) retaining sheet or liquid passage,the driving signal being enough to provide such a quick temperature risebeyond a departure from nucleation boiling point, by which the thermalenergy is provided by the electrothermal transducer to produce filmboiling on the heating portion of the recording head, whereby a bubblecan be formed in the liquid (ink) corresponding to each of the drivingsignals. By the production, development and contraction of the bubble,the liquid (ink) is ejected through an ejection outlet to produce atleast one droplet. The driving signal is preferably in the form of apulse, because the development and contraction of the bubble can beeffected instantaneously, and therefore, the liquid (ink) is ejectedwith quick response. The driving signal in the form of the pulse ispreferably such as disclosed in U.S. Pat. Nos. 4,463,359 and 4,345,262.In addition, the temperature increasing rate of the heating surface ispreferably such as disclosed in U.S. Pat. No. 4,313,124.

The structure of the recording head may be as shown in U.S. Pat. Nos.4,558,333 and 4,459,600 wherein the heating portion is disposed at abent portion, as well as the structure of the combination of theejection outlet, liquid passage and the electrothermal transducer asdisclosed in the above-mentioned patents. In addition, the presentinvention is applicable to the structure disclosed in Japanese Laid-OpenPatent Application No. 123670/1984 wherein a common slit is used as theejection outlet for plural electrothermal transducers, and to thestructure disclosed in Japanese Laid-Open Patent Application No.138461/1984 wherein an opening for absorbing pressure waves of thethermal energy is formed corresponding to the ejecting portion. This isbecause the present invention is effective to perform the recordingoperation with certainty and at a high efficiency regardless of the typeof recording head.

In addition, the present invention is applicable to a serial typerecording head wherein the recording head is fixed on the main assembly,to a replaceable chip type recording head which is connectedelectrically with the main apparatus and which can be supplied with theink when it is mounted in the main assembly, or to a cartridge typerecording head having an integral ink container. The provisions of therecovery means and/or the auxiliary means for the preliminary operationare preferable, because they can further stabilize the effects of thepresent invention. Examples of such means include a capping means forthe recording head, cleaning means therefore, pressing or sucking means,preliminary heating means which may be the electrothermal transducer, anadditional heating element or a combination thereof. Also, means foreffecting preliminary ejection (not for the recording operation) canstabilize the recording operation.

As regards the variation of the recording head mountable, it may be asingle head corresponding to a single color ink, or may be plural headscorresponding to the plurality of ink materials having differentrecording colors or densities. The present invention is effectivelyapplied to an apparatus having at least one of a monochromatic modemainly with black, a multi-color mode with different color ink materialsand/or a full-color mode using the mixture of the colors, which may bean integrally formed recording unit or a combination of plural recordingheads.

Furthermore, in the foregoing embodiments, the ink has been liquid. Italso may be ink material which is solid below the room temperature butliquid at room temperature. Since the ink is kept within a temperaturebetween 30° C. and 70° C., in order to stabilize the viscosity of theink to provide the stabilized ejection in the usual recording apparatusof this type, the ink may be such that it is liquid within thetemperature range when the recording signal is the present invention isapplicable to other types of ink. In one of them, the temperature risedue to the thermal energy is positively prevented by consuming it forthe state change of the ink from the solid state to the liquid State. Another ink material is solidified when it is left, to prevent theevaporation of the ink. In either of the cases, in response to theapplication of the recording signal producing thermal energy, the ink isliquefied, and the liquefied ink may be ejected. Another ink materialmay start to be solidified at the time when it reaches the recordingmaterial. The present invention is also applicable to an ink materialthat is liquefied by the application of the thermal energy. Such an inkmaterial may be retained as a liquid or solid material in through holesor recesses formed in a porous sheet as disclosed in Japanese Laid-OpenPatent Application No. 56847/1979 and Japanese Laid-Open PatentApplication No. 71260/1985. The sheet is faced to the electrothermaltransducers. The most effective one of the techniques described above isthe film boiling system.

The ink jet recording apparatus may be used as an output terminal of aninformation processing apparatus such as a computer or the like, as acopying apparatus combined with an image reader or the like, or as afacsimile machine having information sending and receiving functions.

The present invention can be implemented by supplying a storing mediumcontaining program codes of software executing the steps of the presentinvention into a system or an apparatus wherein the computer, CPU or MPUof the system or the apparatus reads out and executes the program.

In such a case, the program codes constitute the present invention.

The storing medium for supplying the program codes includes, forexample, floppy disk, hard disk, optical disk, magnetoptical disk,CD-ROM, CD-R, magnetic tape, non-volatile memory card and ROM.

Additionally, the present invention can be implemented by an OS(Operating System) running in the computer under the control of theprogram codes to execute a part or entirety of the actual processing.

Further, the present invention can be implemented by writing the programcodes in memory of a function-extended board or unit and then executinga part or entity of the actual processing using the CPU provided in thefunction-extended board or unit.

According to the present invention, the images provided by therespective scans have a reduced complementary relation, so that imagesare formed with incomplete complementary relation, and therefore, evenif the registration due to the physical accuracy error slightly changes,the image density does not significantly change since the influence ofthe change of the registration is lowered.

In the recording operation using the reciprocation main-scanning, thedensity non-uniformity resulting from the difference in the recordingdirections can be reduced. By this, the productivity of textile printingon the recording material such as cotton, silk, Nylon, or polyester canbe increased.

While the invention has been described with reference to the structuresdisclosed herein, it is not confined to the details set forth and thisapplication is intended to cover such modifications or changes as maycome within the purposes of the improvements or the scope of thefollowing claims.

What is claimed is:
 1. An image forming apparatus wherein an image for apredetermined region of a recording material is formed using imageshaving a complementary relation by a plurality of scans of a recordinghead, said apparatus comprising: allocating means for allocatingmulti-level image data for the predetermined region for the scans;gradation reducing means for reducing gradation of the multi-level imagedata allocated by said allocating means; and image forming means forforming an image having the complementary relation by driving saidrecording head in said scans on the basis of the image data havinggradations reduced by said reducing means, wherein the complementaryrelation of the image by said forming means is reduced by at least oneof said allocating means and said gradation reducing means.
 2. Anapparatus according to claim 1, wherein said gradation reducing meansincludes binarizing means.
 3. An apparatus according to claim 1, whereinsaid allocating means allocates the multi-level image data for thepredetermined region for the scans with different ratios.
 4. Anapparatus according to claim 1, wherein said allocating means effectsthe allocation such that a sum of the multi-level image data is morethan 100%.
 5. An apparatus according to claim 4, wherein said allocatingmeans effects the allocation such that a sum of the multi-level imagedata is substantially 100%.
 6. An apparatus according to claim 1,wherein said gradation reducing means reduces gradation of themulti-level image data allocated by said allocating means, throughdifferent processes.
 7. An apparatus according to claim 1, wherein saidgradation reducing means uses an error diffusion method.
 8. An apparatusaccording to claim 7, wherein said gradation reducing means usesdifferent diffusion methods for processing the data.
 9. An apparatusaccording to claim 7, wherein said gradation reducing means usesdifferent thresholds.
 10. An apparatus according to claim 1, whereinsaid recording head ejects ink.
 11. An apparatus according to claim 1,wherein said recording material is textile.
 12. An apparatus accordingto claim 1, wherein said recording head has first and second recordingheads disposed deviated in a sub-scanning direction.
 13. An apparatusaccording to claim 1, wherein said recording head has a plurality ofrecording elements, and the predetermined region is recorded bydifferent recording elements.
 14. An image forming apparatus wherein animage for a predetermined region of a recording material is formed by aplurality of scans of a recording head, said apparatus comprising:allocating means for allocating multi-level image data for thepredetermined region for the scans with different ratios; gradationreducing means for reducing gradation of the multi-level image dataallocated by said allocating means; and image forming means for formingan image having the complementary relation by driving said recordinghead in said scans on the basis of the image data having gradationsreduced by said reducing means.
 15. An image forming apparatus whereinan image for a predetermined region of a recording material is formed bya plurality of scans of a recording head, said apparatus comprising:allocating means for allocating multi-level image data for thepredetermined region for the scans; gradation reducing means forreducing gradation of the multi-level image data allocated by saidallocating means, through different processes; and image forming meansfor forming an image having the complementary relation by driving saidrecording head in said scans on the basis of the image data havinggradations reduced by said reducing means.
 16. An apparatus according toclaim 15, wherein said gradation reducing means uses an error diffusionmethod.
 17. An apparatus according to claim 16, wherein said gradationreducing means uses different diffusion methods for processing the data.18. An apparatus according to claim 16, wherein said gradation reducingmeans uses different thresholds.
 19. An image forming apparatus whereinan image for a predetermined region of a recording material is formed bya plurality of scans of a recording head, said apparatus comprising:allocating means for allocating multi-level image data for thepredetermined region for the scans; gradation reducing means forreducing gradation of the multi-level image data allocated by saidallocating means; and image forming means for forming an image havingthe complementary relation by driving said recording head in said scanson the basis of the image data having gradations reduced by saidreducing means, wherein a correlation in the image by said forming meansis removed by at least one of said allocating means and said gradationreducing means.
 20. An image forming method wherein an image for apredetermined region of a recording material is formed using imageshaving a complementary relation by a plurality of scans of a recordinghead, said method comprising the steps of: processing image data to besupplied to the recording head for the scans to provide an incompletecomplementary relation between images formed by the plurality of scans;and forming an image in the predetermined region by the scans on thebasis of the data processed by said processing step.
 21. An imageforming method wherein an image for a predetermined region of arecording material is formed using images having a complementaryrelation by a plurality of scans of a recording head, said methodcomprising the steps of: processing image data to be supplied to therecording head for the scans to provide an incomplete complementaryrelation between images formed by the plurality of scans; and supplyingto the recording head the data processed by said processing step.
 22. Animage forming method wherein an image for a predetermined region of arecording material is formed by a plurality of scans of a recordinghead, said method comprising the steps of: processing image data to besupplied to the recording head for the scans to remove a correlationbetween images formed by the plurality of scans; and forming an image inthe predetermined region by the scans on the basis of the data processedby said processing step.
 23. An image forming apparatus wherein an imagefor a predetermined region of a recording material is formed by aplurality of scans of a recording head, said apparatus comprising:allocating means for allocating multi-level image data for thepredetermined region for the scans with different ratios; gradationreducing means for reducing gradation of the multi-level image dataallocated by said allocating means through difference processes; andimage forming means for forming an image having the complementaryrelation by driving said recording head in said scans on the basis ofthe image data having gradations reduced by said reducing means.
 24. Anapparatus according to claim 23, wherein said allocating means allocatesthe multi-level image data in a predetermined order.
 25. An apparatusaccording to claim 24, wherein said allocating means allocates themulti-level image data for respective pixels alternatingly.
 26. Anapparatus according to claim 23, wherein said allocating means allocatesthe multi-level image data with attenuation.
 27. An apparatus accordingto claim 23, wherein said allocating means converts the multi-levelimage data for scans with different coefficients.
 28. An apparatusaccording to claim 23, wherein said gradation reducing means includesbinarizing means.
 29. An apparatus according to claim 23, wherein aplurality of such recording heads are provided for multi-colorrecording.
 30. An apparatus according to claim 29, wherein a relativemovement between the provision of recording heads and the recordingmaterial by said scans which are reciprocal and feeding of the recordingmaterial through a predetermined distance, said plurality of recordingheads and allocating means are provided for the colors, and therecording heads are arranged in the scanning direction and the feedingdirection.
 31. An apparatus according to claim 30, wherein saidgradation reducing means effects the operation with different errordiffusion coefficients for the multi-level image data for allocatedportions.
 32. An apparatus according to claim 30, wherein said gradationreducing means effects the operation with different error diffusionpatterns for the multi-level image data for allocated portions.
 33. Anapparatus according to claim 30, wherein said gradation reducing meanseffects it operation with different thresholds of gradation reductiondiffusion patterns for the multi-level image data for allocatedportions.
 34. An apparatus according to claim 30, wherein saidallocating means determines, from a plurality of allocation patterns,allocation for each of the arrays prior to scans by said first andsecond recording heads.
 35. An apparatus according to claim 23, whereinsaid textile includes cotton, silk, nylon, polyester or a mixturethereof.
 36. An apparatus according to claim 23, wherein said recordinghead ejects ink.
 37. An apparatus according to claim 36, wherein saidrecording head ejects the ink by using thermal energy.